22 |
|
* <p> A "main" ForkJoinTask begins execution when submitted to a |
23 |
|
* {@link ForkJoinPool}. Once started, it will usually in turn start |
24 |
|
* other subtasks. As indicated by the name of this class, many |
25 |
< |
* programs using ForkJoinTasks employ only methods <code>fork</code> |
26 |
< |
* and <code>join</code>, or derivatives such as |
27 |
< |
* <code>invokeAll</code>. However, this class also provides a number |
25 |
> |
* programs using ForkJoinTasks employ only methods {@code fork} |
26 |
> |
* and {@code join}, or derivatives such as |
27 |
> |
* {@code invokeAll}. However, this class also provides a number |
28 |
|
* of other methods that can come into play in advanced usages, as |
29 |
|
* well as extension mechanics that allow support of new forms of |
30 |
|
* fork/join processing. |
36 |
|
* operating on purely isolated objects. The primary coordination |
37 |
|
* mechanisms are {@link #fork}, that arranges asynchronous execution, |
38 |
|
* and {@link #join}, that doesn't proceed until the task's result has |
39 |
< |
* been computed. Computations should avoid <code>synchronized</code> |
39 |
> |
* been computed. Computations should avoid {@code synchronized} |
40 |
|
* methods or blocks, and should minimize other blocking |
41 |
|
* synchronization apart from joining other tasks or using |
42 |
|
* synchronizers such as Phasers that are advertised to cooperate with |
48 |
|
* performance, and the potential to indefinitely stall if the number |
49 |
|
* of threads not waiting for IO or other external synchronization |
50 |
|
* becomes exhausted. This usage restriction is in part enforced by |
51 |
< |
* not permitting checked exceptions such as <code>IOExceptions</code> |
51 |
> |
* not permitting checked exceptions such as {@code IOExceptions} |
52 |
|
* to be thrown. However, computations may still encounter unchecked |
53 |
|
* exceptions, that are rethrown to callers attempting join |
54 |
|
* them. These exceptions may additionally include |
58 |
|
* <p>The primary method for awaiting completion and extracting |
59 |
|
* results of a task is {@link #join}, but there are several variants: |
60 |
|
* The {@link Future#get} methods support interruptible and/or timed |
61 |
< |
* waits for completion and report results using <code>Future</code> |
61 |
> |
* waits for completion and report results using {@code Future} |
62 |
|
* conventions. Method {@link #helpJoin} enables callers to actively |
63 |
|
* execute other tasks while awaiting joins, which is sometimes more |
64 |
|
* efficient but only applies when all subtasks are known to be |
65 |
|
* strictly tree-structured. Method {@link #invoke} is semantically |
66 |
< |
* equivalent to <code>fork(); join()</code> but always attempts to |
66 |
> |
* equivalent to {@code fork(); join()} but always attempts to |
67 |
|
* begin execution in the current thread. The "<em>quiet</em>" forms |
68 |
|
* of these methods do not extract results or report exceptions. These |
69 |
|
* may be useful when a set of tasks are being executed, and you need |
70 |
|
* to delay processing of results or exceptions until all complete. |
71 |
< |
* Method <code>invokeAll</code> (available in multiple versions) |
71 |
> |
* Method {@code invokeAll} (available in multiple versions) |
72 |
|
* performs the most common form of parallel invocation: forking a set |
73 |
|
* of tasks and joining them all. |
74 |
|
* |
76 |
|
* Instead, you subclass one of the abstract classes that support a |
77 |
|
* particular style of fork/join processing. Normally, a concrete |
78 |
|
* ForkJoinTask subclass declares fields comprising its parameters, |
79 |
< |
* established in a constructor, and then defines a <code>compute</code> |
79 |
> |
* established in a constructor, and then defines a {@code compute} |
80 |
|
* method that somehow uses the control methods supplied by this base |
81 |
< |
* class. While these methods have <code>public</code> access (to allow |
81 |
> |
* class. While these methods have {@code public} access (to allow |
82 |
|
* instances of different task subclasses to call each others |
83 |
|
* methods), some of them may only be called from within other |
84 |
|
* ForkJoinTasks. Attempts to invoke them in other contexts result in |
85 |
|
* exceptions or errors possibly including ClassCastException. |
86 |
|
* |
87 |
< |
* <p>Most base support methods are <code>final</code> because their |
87 |
> |
* <p>Most base support methods are {@code final} because their |
88 |
|
* implementations are intrinsically tied to the underlying |
89 |
|
* lightweight task scheduling framework, and so cannot be overridden. |
90 |
|
* Developers creating new basic styles of fork/join processing should |
91 |
< |
* minimally implement <code>protected</code> methods |
92 |
< |
* <code>exec</code>, <code>setRawResult</code>, and |
93 |
< |
* <code>getRawResult</code>, while also introducing an abstract |
91 |
> |
* minimally implement {@code protected} methods |
92 |
> |
* {@code exec}, {@code setRawResult}, and |
93 |
> |
* {@code getRawResult}, while also introducing an abstract |
94 |
|
* computational method that can be implemented in its subclasses, |
95 |
< |
* possibly relying on other <code>protected</code> methods provided |
95 |
> |
* possibly relying on other {@code protected} methods provided |
96 |
|
* by this class. |
97 |
|
* |
98 |
|
* <p>ForkJoinTasks should perform relatively small amounts of |
99 |
< |
* computations, othewise splitting into smaller tasks. As a very |
99 |
> |
* computations, otherwise splitting into smaller tasks. As a very |
100 |
|
* rough rule of thumb, a task should perform more than 100 and less |
101 |
|
* than 10000 basic computational steps. If tasks are too big, then |
102 |
< |
* parellelism cannot improve throughput. If too small, then memory |
102 |
> |
* parallelism cannot improve throughput. If too small, then memory |
103 |
|
* and internal task maintenance overhead may overwhelm processing. |
104 |
|
* |
105 |
< |
* <p>ForkJoinTasks are <code>Serializable</code>, which enables them |
105 |
> |
* <p>ForkJoinTasks are {@code Serializable}, which enables them |
106 |
|
* to be used in extensions such as remote execution frameworks. It is |
107 |
|
* in general sensible to serialize tasks only before or after, but |
108 |
|
* not during execution. Serialization is not relied on during |
128 |
|
* currently unused. Also value 0x80000000 is available as spare |
129 |
|
* completion value. |
130 |
|
*/ |
131 |
< |
volatile int status; // accessed directy by pool and workers |
131 |
> |
volatile int status; // accessed directly by pool and workers |
132 |
|
|
133 |
|
static final int COMPLETION_MASK = 0xe0000000; |
134 |
|
static final int NORMAL = 0xe0000000; // == mask |
141 |
|
/** |
142 |
|
* Table of exceptions thrown by tasks, to enable reporting by |
143 |
|
* callers. Because exceptions are rare, we don't directly keep |
144 |
< |
* them with task objects, but instead us a weak ref table. Note |
144 |
> |
* them with task objects, but instead use a weak ref table. Note |
145 |
|
* that cancellation exceptions don't appear in the table, but are |
146 |
|
* instead recorded as status values. |
147 |
< |
* Todo: Use ConcurrentReferenceHashMap |
147 |
> |
* TODO: Use ConcurrentReferenceHashMap |
148 |
|
*/ |
149 |
|
static final Map<ForkJoinTask<?>, Throwable> exceptionMap = |
150 |
|
Collections.synchronizedMap |
153 |
|
// within-package utilities |
154 |
|
|
155 |
|
/** |
156 |
< |
* Get current worker thread, or null if not a worker thread |
156 |
> |
* Gets current worker thread, or null if not a worker thread. |
157 |
|
*/ |
158 |
|
static ForkJoinWorkerThread getWorker() { |
159 |
|
Thread t = Thread.currentThread(); |
176 |
|
// Setting completion status |
177 |
|
|
178 |
|
/** |
179 |
< |
* Mark completion and wake up threads waiting to join this task. |
179 |
> |
* Marks completion and wakes up threads waiting to join this task. |
180 |
> |
* |
181 |
|
* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
182 |
|
*/ |
183 |
|
final void setCompletion(int completion) { |
256 |
|
/** |
257 |
|
* Sets status to indicate there is joiner, then waits for join, |
258 |
|
* surrounded with pool notifications. |
259 |
+ |
* |
260 |
|
* @return status upon exit |
261 |
|
*/ |
262 |
|
private int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) { |
299 |
|
} |
300 |
|
|
301 |
|
/** |
302 |
< |
* Notify pool that thread is unblocked. Called by signalled |
302 |
> |
* Notifies pool that thread is unblocked. Called by signalled |
303 |
|
* threads when woken by non-FJ threads (which is atypical). |
304 |
|
*/ |
305 |
|
private void adjustPoolCountsOnUnblock(ForkJoinPool pool) { |
310 |
|
} |
311 |
|
|
312 |
|
/** |
313 |
< |
* Notify pool to adjust counts on cancelled or timed out wait |
313 |
> |
* Notifies pool to adjust counts on cancelled or timed out wait. |
314 |
|
*/ |
315 |
|
private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) { |
316 |
|
if (pool != null) { |
325 |
|
} |
326 |
|
|
327 |
|
/** |
328 |
< |
* Handle interruptions during waits. |
328 |
> |
* Handles interruptions during waits. |
329 |
|
*/ |
330 |
|
private void onInterruptedWait() { |
331 |
|
ForkJoinWorkerThread w = getWorker(); |
344 |
|
} |
345 |
|
|
346 |
|
/** |
347 |
< |
* Throws the exception associated with status s; |
347 |
> |
* Throws the exception associated with status s. |
348 |
> |
* |
349 |
|
* @throws the exception |
350 |
|
*/ |
351 |
|
private void reportException(int s) { |
358 |
|
} |
359 |
|
|
360 |
|
/** |
361 |
< |
* Returns result or throws exception using j.u.c.Future conventions |
361 |
> |
* Returns result or throws exception using j.u.c.Future conventions. |
362 |
|
* Only call when isDone known to be true. |
363 |
|
*/ |
364 |
|
private V reportFutureResult() |
378 |
|
|
379 |
|
/** |
380 |
|
* Returns result or throws exception using j.u.c.Future conventions |
381 |
< |
* with timeouts |
381 |
> |
* with timeouts. |
382 |
|
*/ |
383 |
|
private V reportTimedFutureResult() |
384 |
|
throws InterruptedException, ExecutionException, TimeoutException { |
399 |
|
|
400 |
|
/** |
401 |
|
* Calls exec, recording completion, and rethrowing exception if |
402 |
< |
* encountered. Caller should normally check status before calling |
402 |
> |
* encountered. Caller should normally check status before calling. |
403 |
> |
* |
404 |
|
* @return true if completed normally |
405 |
|
*/ |
406 |
|
private boolean tryExec() { |
418 |
|
|
419 |
|
/** |
420 |
|
* Main execution method used by worker threads. Invokes |
421 |
< |
* base computation unless already complete |
421 |
> |
* base computation unless already complete. |
422 |
|
*/ |
423 |
|
final void quietlyExec() { |
424 |
|
if (status >= 0) { |
434 |
|
} |
435 |
|
|
436 |
|
/** |
437 |
< |
* Calls exec, recording but not rethrowing exception |
438 |
< |
* Caller should normally check status before calling |
437 |
> |
* Calls exec(), recording but not rethrowing exception. |
438 |
> |
* Caller should normally check status before calling. |
439 |
> |
* |
440 |
|
* @return true if completed normally |
441 |
|
*/ |
442 |
|
private boolean tryQuietlyInvoke() { |
452 |
|
} |
453 |
|
|
454 |
|
/** |
455 |
< |
* Cancel, ignoring any exceptions it throws |
455 |
> |
* Cancels, ignoring any exceptions it throws. |
456 |
|
*/ |
457 |
|
final void cancelIgnoringExceptions() { |
458 |
|
try { |
488 |
|
|
489 |
|
/** |
490 |
|
* Returns the result of the computation when it is ready. |
491 |
< |
* This method differs from <code>get</code> in that abnormal |
491 |
> |
* This method differs from {@code get} in that abnormal |
492 |
|
* completion results in RuntimeExceptions or Errors, not |
493 |
|
* ExecutionExceptions. |
494 |
|
* |
504 |
|
/** |
505 |
|
* Commences performing this task, awaits its completion if |
506 |
|
* necessary, and return its result. |
507 |
+ |
* |
508 |
|
* @throws Throwable (a RuntimeException, Error, or unchecked |
509 |
< |
* exception) if the underlying computation did so. |
509 |
> |
* exception) if the underlying computation did so |
510 |
|
* @return the computed result |
511 |
|
*/ |
512 |
|
public final V invoke() { |
517 |
|
} |
518 |
|
|
519 |
|
/** |
520 |
< |
* Forks both tasks, returning when <code>isDone</code> holds for |
520 |
> |
* Forks both tasks, returning when {@code isDone} holds for |
521 |
|
* both of them or an exception is encountered. This method may be |
522 |
|
* invoked only from within ForkJoinTask computations. Attempts to |
523 |
|
* invoke in other contexts result in exceptions or errors |
524 |
|
* possibly including ClassCastException. |
525 |
+ |
* |
526 |
|
* @param t1 one task |
527 |
|
* @param t2 the other task |
528 |
|
* @throws NullPointerException if t1 or t2 are null |
529 |
< |
* @throws RuntimeException or Error if either task did so. |
529 |
> |
* @throws RuntimeException or Error if either task did so |
530 |
|
*/ |
531 |
|
public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) { |
532 |
|
t2.fork(); |
535 |
|
} |
536 |
|
|
537 |
|
/** |
538 |
< |
* Forks the given tasks, returning when <code>isDone</code> holds |
538 |
> |
* Forks the given tasks, returning when {@code isDone} holds |
539 |
|
* for all of them. If any task encounters an exception, others |
540 |
|
* may be cancelled. This method may be invoked only from within |
541 |
|
* ForkJoinTask computations. Attempts to invoke in other contexts |
542 |
|
* result in exceptions or errors possibly including ClassCastException. |
543 |
+ |
* |
544 |
|
* @param tasks the array of tasks |
545 |
< |
* @throws NullPointerException if tasks or any element are null. |
546 |
< |
* @throws RuntimeException or Error if any task did so. |
545 |
> |
* @throws NullPointerException if tasks or any element are null |
546 |
> |
* @throws RuntimeException or Error if any task did so |
547 |
|
*/ |
548 |
|
public static void invokeAll(ForkJoinTask<?>... tasks) { |
549 |
|
Throwable ex = null; |
580 |
|
|
581 |
|
/** |
582 |
|
* Forks all tasks in the collection, returning when |
583 |
< |
* <code>isDone</code> holds for all of them. If any task |
583 |
> |
* {@code isDone} holds for all of them. If any task |
584 |
|
* encounters an exception, others may be cancelled. This method |
585 |
|
* may be invoked only from within ForkJoinTask |
586 |
< |
* computations. Attempts to invoke in other contexts resul!t in |
586 |
> |
* computations. Attempts to invoke in other contexts result in |
587 |
|
* exceptions or errors possibly including ClassCastException. |
588 |
+ |
* |
589 |
|
* @param tasks the collection of tasks |
590 |
< |
* @throws NullPointerException if tasks or any element are null. |
591 |
< |
* @throws RuntimeException or Error if any task did so. |
590 |
> |
* @throws NullPointerException if tasks or any element are null |
591 |
> |
* @throws RuntimeException or Error if any task did so |
592 |
|
*/ |
593 |
|
public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) { |
594 |
|
if (!(tasks instanceof List)) { |
632 |
|
/** |
633 |
|
* Returns true if the computation performed by this task has |
634 |
|
* completed (or has been cancelled). |
635 |
+ |
* |
636 |
|
* @return true if this computation has completed |
637 |
|
*/ |
638 |
|
public final boolean isDone() { |
641 |
|
|
642 |
|
/** |
643 |
|
* Returns true if this task was cancelled. |
644 |
+ |
* |
645 |
|
* @return true if this task was cancelled |
646 |
|
*/ |
647 |
|
public final boolean isCancelled() { |
650 |
|
|
651 |
|
/** |
652 |
|
* Asserts that the results of this task's computation will not be |
653 |
< |
* used. If a cancellation occurs before atempting to execute this |
654 |
< |
* task, then execution will be suppressed, <code>isCancelled</code> |
655 |
< |
* will report true, and <code>join</code> will result in a |
656 |
< |
* <code>CancellationException</code> being thrown. Otherwise, when |
653 |
> |
* used. If a cancellation occurs before attempting to execute this |
654 |
> |
* task, then execution will be suppressed, {@code isCancelled} |
655 |
> |
* will report true, and {@code join} will result in a |
656 |
> |
* {@code CancellationException} being thrown. Otherwise, when |
657 |
|
* cancellation races with completion, there are no guarantees |
658 |
< |
* about whether <code>isCancelled</code> will report true, whether |
659 |
< |
* <code>join</code> will return normally or via an exception, or |
658 |
> |
* about whether {@code isCancelled} will report true, whether |
659 |
> |
* {@code join} will return normally or via an exception, or |
660 |
|
* whether these behaviors will remain consistent upon repeated |
661 |
|
* invocation. |
662 |
|
* |
667 |
|
* <p> This method is designed to be invoked by <em>other</em> |
668 |
|
* tasks. To terminate the current task, you can just return or |
669 |
|
* throw an unchecked exception from its computation method, or |
670 |
< |
* invoke <code>completeExceptionally</code>. |
670 |
> |
* invoke {@code completeExceptionally}. |
671 |
|
* |
672 |
|
* @param mayInterruptIfRunning this value is ignored in the |
673 |
|
* default implementation because tasks are not in general |
681 |
|
} |
682 |
|
|
683 |
|
/** |
684 |
< |
* Returns true if this task threw an exception or was cancelled |
684 |
> |
* Returns true if this task threw an exception or was cancelled. |
685 |
> |
* |
686 |
|
* @return true if this task threw an exception or was cancelled |
687 |
|
*/ |
688 |
|
public final boolean isCompletedAbnormally() { |
693 |
|
* Returns the exception thrown by the base computation, or a |
694 |
|
* CancellationException if cancelled, or null if none or if the |
695 |
|
* method has not yet completed. |
696 |
+ |
* |
697 |
|
* @return the exception, or null if none |
698 |
|
*/ |
699 |
|
public final Throwable getException() { |
708 |
|
/** |
709 |
|
* Completes this task abnormally, and if not already aborted or |
710 |
|
* cancelled, causes it to throw the given exception upon |
711 |
< |
* <code>join</code> and related operations. This method may be used |
711 |
> |
* {@code join} and related operations. This method may be used |
712 |
|
* to induce exceptions in asynchronous tasks, or to force |
713 |
|
* completion of tasks that would not otherwise complete. Its use |
714 |
|
* in other situations is likely to be wrong. This method is |
715 |
< |
* overridable, but overridden versions must invoke <code>super</code> |
715 |
> |
* overridable, but overridden versions must invoke {@code super} |
716 |
|
* implementation to maintain guarantees. |
717 |
|
* |
718 |
|
* @param ex the exception to throw. If this exception is |
727 |
|
|
728 |
|
/** |
729 |
|
* Completes this task, and if not already aborted or cancelled, |
730 |
< |
* returning a <code>null</code> result upon <code>join</code> and related |
730 |
> |
* returning a {@code null} result upon {@code join} and related |
731 |
|
* operations. This method may be used to provide results for |
732 |
|
* asynchronous tasks, or to provide alternative handling for |
733 |
|
* tasks that would not otherwise complete normally. Its use in |
734 |
|
* other situations is likely to be wrong. This method is |
735 |
< |
* overridable, but overridden versions must invoke <code>super</code> |
735 |
> |
* overridable, but overridden versions must invoke {@code super} |
736 |
|
* implementation to maintain guarantees. |
737 |
|
* |
738 |
< |
* @param value the result value for this task. |
738 |
> |
* @param value the result value for this task |
739 |
|
*/ |
740 |
|
public void complete(V value) { |
741 |
|
try { |
765 |
|
/** |
766 |
|
* Possibly executes other tasks until this task is ready, then |
767 |
|
* returns the result of the computation. This method may be more |
768 |
< |
* efficient than <code>join</code>, but is only applicable when |
769 |
< |
* there are no potemtial dependencies between continuation of the |
768 |
> |
* efficient than {@code join}, but is only applicable when |
769 |
> |
* there are no potential dependencies between continuation of the |
770 |
|
* current task and that of any other task that might be executed |
771 |
|
* while helping. (This usually holds for pure divide-and-conquer |
772 |
|
* tasks). This method may be invoked only from within |
773 |
|
* ForkJoinTask computations. Attempts to invoke in other contexts |
774 |
< |
* resul!t in exceptions or errors possibly including ClassCastException. |
774 |
> |
* result in exceptions or errors possibly including ClassCastException. |
775 |
> |
* |
776 |
|
* @return the computed result |
777 |
|
*/ |
778 |
|
public final V helpJoin() { |
785 |
|
/** |
786 |
|
* Possibly executes other tasks until this task is ready. This |
787 |
|
* method may be invoked only from within ForkJoinTask |
788 |
< |
* computations. Attempts to invoke in other contexts resul!t in |
788 |
> |
* computations. Attempts to invoke in other contexts result in |
789 |
|
* exceptions or errors possibly including ClassCastException. |
790 |
|
*/ |
791 |
|
public final void quietlyHelpJoin() { |
836 |
|
|
837 |
|
/** |
838 |
|
* Resets the internal bookkeeping state of this task, allowing a |
839 |
< |
* subsequent <code>fork</code>. This method allows repeated reuse of |
839 |
> |
* subsequent {@code fork}. This method allows repeated reuse of |
840 |
|
* this task, but only if reuse occurs when this task has either |
841 |
|
* never been forked, or has been forked, then completed and all |
842 |
|
* outstanding joins of this task have also completed. Effects |
853 |
|
/** |
854 |
|
* Returns the pool hosting the current task execution, or null |
855 |
|
* if this task is executing outside of any pool. |
856 |
< |
* @return the pool, or null if none. |
856 |
> |
* |
857 |
> |
* @return the pool, or null if none |
858 |
|
*/ |
859 |
|
public static ForkJoinPool getPool() { |
860 |
|
Thread t = Thread.currentThread(); |
871 |
|
* were not, stolen. This method may be invoked only from within |
872 |
|
* ForkJoinTask computations. Attempts to invoke in other contexts |
873 |
|
* result in exceptions or errors possibly including ClassCastException. |
874 |
+ |
* |
875 |
|
* @return true if unforked |
876 |
|
*/ |
877 |
|
public boolean tryUnfork() { |
883 |
|
* forked by the current worker thread but not yet executed. This |
884 |
|
* value may be useful for heuristic decisions about whether to |
885 |
|
* fork other tasks. |
886 |
+ |
* |
887 |
|
* @return the number of tasks |
888 |
|
*/ |
889 |
|
public static int getQueuedTaskCount() { |
892 |
|
} |
893 |
|
|
894 |
|
/** |
895 |
< |
* Returns a estimate of how many more locally queued tasks are |
895 |
> |
* Returns an estimate of how many more locally queued tasks are |
896 |
|
* held by the current worker thread than there are other worker |
897 |
|
* threads that might steal them. This value may be useful for |
898 |
|
* heuristic decisions about whether to fork other tasks. In many |
900 |
|
* aim to maintain a small constant surplus (for example, 3) of |
901 |
|
* tasks, and to process computations locally if this threshold is |
902 |
|
* exceeded. |
903 |
+ |
* |
904 |
|
* @return the surplus number of tasks, which may be negative |
905 |
|
*/ |
906 |
|
public static int getSurplusQueuedTaskCount() { |
911 |
|
// Extension methods |
912 |
|
|
913 |
|
/** |
914 |
< |
* Returns the result that would be returned by <code>join</code>, |
914 |
> |
* Returns the result that would be returned by {@code join}, |
915 |
|
* even if this task completed abnormally, or null if this task is |
916 |
|
* not known to have been completed. This method is designed to |
917 |
|
* aid debugging, as well as to support extensions. Its use in any |
918 |
|
* other context is discouraged. |
919 |
|
* |
920 |
< |
* @return the result, or null if not completed. |
920 |
> |
* @return the result, or null if not completed |
921 |
|
*/ |
922 |
|
public abstract V getRawResult(); |
923 |
|
|
936 |
|
* called otherwise. The return value controls whether this task |
937 |
|
* is considered to be done normally. It may return false in |
938 |
|
* asynchronous actions that require explicit invocations of |
939 |
< |
* <code>complete</code> to become joinable. It may throw exceptions |
939 |
> |
* {@code complete} to become joinable. It may throw exceptions |
940 |
|
* to indicate abnormal exit. |
941 |
+ |
* |
942 |
|
* @return true if completed normally |
943 |
|
* @throws Error or RuntimeException if encountered during computation |
944 |
|
*/ |
945 |
|
protected abstract boolean exec(); |
946 |
|
|
947 |
|
/** |
948 |
< |
* Returns, but does not unschedule or execute, the task most |
949 |
< |
* recently forked by the current thread but not yet executed, if |
950 |
< |
* one is available. There is no guarantee that this task will |
951 |
< |
* actually be polled or executed next. |
952 |
< |
* This method is designed primarily to support extensions, |
953 |
< |
* and is unlikely to be useful otherwise. |
954 |
< |
* This method may be invoked only from within |
955 |
< |
* ForkJoinTask computations. Attempts to invoke in other contexts |
937 |
< |
* result in exceptions or errors possibly including ClassCastException. |
948 |
> |
* Returns, but does not unschedule or execute, the task queued by |
949 |
> |
* the current thread but not yet executed, if one is |
950 |
> |
* available. There is no guarantee that this task will actually |
951 |
> |
* be polled or executed next. This method is designed primarily |
952 |
> |
* to support extensions, and is unlikely to be useful otherwise. |
953 |
> |
* This method may be invoked only from within ForkJoinTask |
954 |
> |
* computations. Attempts to invoke in other contexts result in |
955 |
> |
* exceptions or errors possibly including ClassCastException. |
956 |
|
* |
957 |
|
* @return the next task, or null if none are available |
958 |
|
*/ |
961 |
|
} |
962 |
|
|
963 |
|
/** |
964 |
< |
* Unschedules and returns, without executing, the task most |
965 |
< |
* recently forked by the current thread but not yet executed. |
966 |
< |
* This method is designed primarily to support extensions, |
967 |
< |
* and is unlikely to be useful otherwise. |
968 |
< |
* This method may be invoked only from within |
969 |
< |
* ForkJoinTask computations. Attempts to invoke in other contexts |
970 |
< |
* result in exceptions or errors possibly including ClassCastException. |
964 |
> |
* Unschedules and returns, without executing, the next task |
965 |
> |
* queued by the current thread but not yet executed. This method |
966 |
> |
* is designed primarily to support extensions, and is unlikely to |
967 |
> |
* be useful otherwise. This method may be invoked only from |
968 |
> |
* within ForkJoinTask computations. Attempts to invoke in other |
969 |
> |
* contexts result in exceptions or errors possibly including |
970 |
> |
* ClassCastException. |
971 |
|
* |
972 |
|
* @return the next task, or null if none are available |
973 |
|
*/ |
974 |
|
protected static ForkJoinTask<?> pollNextLocalTask() { |
975 |
< |
return ((ForkJoinWorkerThread)(Thread.currentThread())).popTask(); |
975 |
> |
return ((ForkJoinWorkerThread)(Thread.currentThread())).pollLocalTask(); |
976 |
|
} |
977 |
|
|
978 |
|
/** |
979 |
< |
* Unschedules and returns, without executing, the task most |
980 |
< |
* recently forked by the current thread but not yet executed, if |
981 |
< |
* one is available, or if not available, a task that was forked |
982 |
< |
* by some other thread, if available. Availability may be |
983 |
< |
* transient, so a <code>null</code> result does not necessarily |
984 |
< |
* imply quiecence of the pool this task is operating in. |
985 |
< |
* This method is designed primarily to support extensions, |
986 |
< |
* and is unlikely to be useful otherwise. |
969 |
< |
* This method may be invoked only from within |
979 |
> |
* Unschedules and returns, without executing, the next task |
980 |
> |
* queued by the current thread but not yet executed, if one is |
981 |
> |
* available, or if not available, a task that was forked by some |
982 |
> |
* other thread, if available. Availability may be transient, so a |
983 |
> |
* {@code null} result does not necessarily imply quiescence |
984 |
> |
* of the pool this task is operating in. This method is designed |
985 |
> |
* primarily to support extensions, and is unlikely to be useful |
986 |
> |
* otherwise. This method may be invoked only from within |
987 |
|
* ForkJoinTask computations. Attempts to invoke in other contexts |
988 |
< |
* result in exceptions or errors possibly including ClassCastException. |
988 |
> |
* result in exceptions or errors possibly including |
989 |
> |
* ClassCastException. |
990 |
|
* |
991 |
|
* @return a task, or null if none are available |
992 |
|
*/ |
1003 |
|
* Save the state to a stream. |
1004 |
|
* |
1005 |
|
* @serialData the current run status and the exception thrown |
1006 |
< |
* during execution, or null if none. |
1006 |
> |
* during execution, or null if none |
1007 |
|
* @param s the stream |
1008 |
|
*/ |
1009 |
|
private void writeObject(java.io.ObjectOutputStream s) |
1014 |
|
|
1015 |
|
/** |
1016 |
|
* Reconstitute the instance from a stream. |
1017 |
+ |
* |
1018 |
|
* @param s the stream |
1019 |
|
*/ |
1020 |
|
private void readObject(java.io.ObjectInputStream s) |
1028 |
|
} |
1029 |
|
|
1030 |
|
// Temporary Unsafe mechanics for preliminary release |
1031 |
+ |
private static Unsafe getUnsafe() throws Throwable { |
1032 |
+ |
try { |
1033 |
+ |
return Unsafe.getUnsafe(); |
1034 |
+ |
} catch (SecurityException se) { |
1035 |
+ |
try { |
1036 |
+ |
return java.security.AccessController.doPrivileged |
1037 |
+ |
(new java.security.PrivilegedExceptionAction<Unsafe>() { |
1038 |
+ |
public Unsafe run() throws Exception { |
1039 |
+ |
return getUnsafePrivileged(); |
1040 |
+ |
}}); |
1041 |
+ |
} catch (java.security.PrivilegedActionException e) { |
1042 |
+ |
throw e.getCause(); |
1043 |
+ |
} |
1044 |
+ |
} |
1045 |
+ |
} |
1046 |
+ |
|
1047 |
+ |
private static Unsafe getUnsafePrivileged() |
1048 |
+ |
throws NoSuchFieldException, IllegalAccessException { |
1049 |
+ |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
1050 |
+ |
f.setAccessible(true); |
1051 |
+ |
return (Unsafe) f.get(null); |
1052 |
+ |
} |
1053 |
+ |
|
1054 |
+ |
private static long fieldOffset(String fieldName) |
1055 |
+ |
throws NoSuchFieldException { |
1056 |
+ |
return _unsafe.objectFieldOffset |
1057 |
+ |
(ForkJoinTask.class.getDeclaredField(fieldName)); |
1058 |
+ |
} |
1059 |
|
|
1060 |
|
static final Unsafe _unsafe; |
1061 |
|
static final long statusOffset; |
1062 |
|
|
1063 |
|
static { |
1064 |
|
try { |
1065 |
< |
if (ForkJoinTask.class.getClassLoader() != null) { |
1066 |
< |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
1067 |
< |
f.setAccessible(true); |
1068 |
< |
_unsafe = (Unsafe)f.get(null); |
1069 |
< |
} |
1023 |
< |
else |
1024 |
< |
_unsafe = Unsafe.getUnsafe(); |
1025 |
< |
statusOffset = _unsafe.objectFieldOffset |
1026 |
< |
(ForkJoinTask.class.getDeclaredField("status")); |
1027 |
< |
} catch (Exception ex) { throw new Error(ex); } |
1065 |
> |
_unsafe = getUnsafe(); |
1066 |
> |
statusOffset = fieldOffset("status"); |
1067 |
> |
} catch (Throwable e) { |
1068 |
> |
throw new RuntimeException("Could not initialize intrinsics", e); |
1069 |
> |
} |
1070 |
|
} |
1071 |
|
|
1072 |
|
} |